Hrunalaug is a small hot spring close to the town Flúðir in south-west of Iceland. This natural spring is an old stone-walled pool, very small but warm and cozy to relax and enjoy the nature. There is a small shelter next to the pool that can be used to change. 

The hot spring is on a private property and it is very important to be respectful to the nature and don’t leave anything behind and there is absolutely no camping there!

Directions

From Reykjavík it is about 80 minutes drive to Flúðir. Before you arrive in Flúðir take road number 344 with the sign Hruni. You drive about 3 km (1.2 miles) before taking road number 345 also with the sign Hruni and when you see a small sign on your right side saying Sólheimar you turn again. From there you drive for about 400 meters (0.26 miles) until you see a parking area with a no camping sign on your left. From the parking lot walk about 5 minutes to the hot spring.
Read more about Driving in Iceland.